Termination or joint for high tension electrical cables



TERMINATION OR JOINT FOR HIGH TENSION ELECTRICAL GABLES Oct. 29, 1940.J. K WEBB ET AL Filed Aug. 12, 1956 F ig. 2.

RC. M/LD/VEA WW Patented Oct. 29, 1940 UNITED STATES PATENT OFFICETERMINATION OR JOINT FOR HIGH TENSION ELECTRICAL CABLES York, N. Y.

Application August 12, 1936, Serial No. 95,544

1 Claim.

This invention relates to terminations or joints for high tension cablesand is a modification of the invention disclosed in United States PatentNo. 1,935,820, issued November 21, 1933. In that 5 patent we havedescribed a condenser stress cone arrangement for grading the stressbetween the core and the sheath of the cable in which the cone islocated with its base directed towards the end of the cable on which thecone is applied, the conductive layer at the base being at corepotential.

Difliculty is sometimes experienced in applying this arrangement toexisting types of terminations in which the porcelain sealing chamber isof conical form. with its base directed away from the end of the cableowing to the fact that there is insufficient room in the apex of thesealing chamber to accommodate the base of the cone. Moreover in makingjoints with the bases of the cones directed towards the centre of thejoint there is difilculty in applying insulation to the joint by theusual process of applying an overall insulating roll.

The above objections are overcome by the pres- 25 ent invention whichprovides a high tension cable joint or termination in which a hollowself-supporting conical condenser comprising insulation separatedconductive layers is fitted over the end of the cable insulation withits base directed away from the cable end towards the sheath but spacedtherefrom. The conductive layer at the apex of the cone may be connectedto the core and that at the base of the cone may be connected to earththrough a low impedance connection whereby an effective grading of thepotential is obtained. The conditions for uniform gradient with thisarrangement of cone are somewhat different from those set forth in theprior patent, and to obtain optimum results the design of the cone mustbe slightly modified in respect of the number and size of the foils.

The invention will be better understood by reference to the accompanyingdrawing in which: 45 Fig. 1 is a sectional diagram of a cabletermination constructed according to the invention;

Fig. 2 is a sectional diagram of a cable joint constructed according tothe invention.

Referring to Fig. 1 the cable sheath is indicated at I which is cut awayto expose the cable insulation 2 in the usual manner and 3 is the cablecore or conductor connected to the terminal device 4 mounted on theporcelain sealing bell 5.

The condenser cone 8 comprises a metal tube 55 former I at the apex endsupporting a. number of insulation separated conductive layers 8 01gradually increasing diameter as described in our aforesaid patentspecification. The metal tube former is slipped over the cableinsulation 2 so that the cone 6 extends with its base 9 directed awayfrom the conductor 3 and towards the cable 5 sheath I as shown. Theconductive layer at the base of the cone is maintained at earth or lowpotential whereas the conductive layer or metal former at the apex is athigh potential, thus securing a capacity grading effect within the ter-10 mination. As indicated in the drawing electrical connections In and II may be provided respec tively between the conductor 3 and the metalformer I and between the sheath I and the conductive layer at the baseof the cone.

The sealing bell would be filled with insulating compound in the usualmanner and if desired polymerised styrene may be applied to insulate thecone and isolate the compound in the termination from that in the cableby the methods forming the subject matter of our application UnitedStates application Ser. No. 35,960, filed August 13, 1935.

The construction of the joint illustrated in Fig. 2 will be apparentfrom the drawing in which 2 the parts already described in connectionwith Fig. 1 are indicated by the same reference numerals. In this jointthe conductors 3 are joined by means of a ferrule I2 in the usual mannerafter the condenser cones 6 have been applied and paper insulation I3 islapped on to extend over the cones. The joint is completed by a leadsleeve I4 in the usual manner and if desired polymerised styrene may beapplied to insulate the joint and the cones in accordance with themethods forming the subject matter of our Patent No. 2,105,567.

What is claimed is:

A high tension cable comprising a conductor, an insulating layer and ametallic sheath about said insulating layer, said conductor, insulatinglayer and sheath each being of substantially uniform cross-secti0n, apotential grading means for said cable consisting of a hollowself-supporting frusto conical condenser comprising insula- 4 tionseparated conductive layers, the small end of said condenser fittingsnugly over said insulating layer, and being arranged with the base ofsaid frusto-conical condenser directed away from the end of saidconductor and toward said sheath, but spaced therefrom, and means forconnecting the end layers of said condenser to the conductor and thecable sheath, respectively.

JOHN KRAUSS WEBB. RAYMOND CHARLES LIIIIDNER.

